I recommend using YouTube instead of Facebook for good reasons. One is that YouTube is designed for video-sharing and video-streaming contents.. This means that the quality of your video is not affected because the system itself is for streaming. On the other hand, Facebook is designed to be the "Jack of all trades" when it comes to social interaction. Yes, you can post pictures, videos and links on Facebook, but the drawback is that, the quality is somehow affected to compensate on other people's screens. That is why when you post your pictures or videos on Facebook, you'll notice some changes in the quality.
My advise is, post your vlogs on YouTube first and then generate some view with the use of other social networks (e.g. Facebook and Twitter).